Electronic correlations, layer distinction, and electron doping in alternating single-layer trilayer La₃Ni₂O₇ polymorph

The discovery of high-temperature superconductivity (Tc ~ 80 K) in pressurized bilayer Ruddlesden-Popper (RP) nickelate La₃Ni₂O₇ has sparked significant theoretical and experimental interest. Recently, a new polymorph of La₃Ni₂O₇ with an alternating stacking sequence of single-layer and trilayer blocks (1313) has been identified. Using density-functional theory plus dynamical mean-field theory (DFT+DMFT), we investigate the correlated electronic structure of this 1313 polymorph, which becomes superconducting under pressure. At ambient pressure, the single-layer block is Mott insulating, and the low-energy physics is governed by the trilayer block. Upon applying pressure, the Mott gap in the single-layer block closes due to orbital-selective physics, facilitating charge transfer to the trilayer block. This effective doping of the trilayer may explain the higher Tc (~80 K) observed in La₃Ni₂O₇-1313 compared to the nominal trilayer La₄Ni₃O₁₀ (~30 K). We propose that this correlation-driven layer differentiation is key to understanding the superconductivity in the La₃Ni₂O₇ polymorph and that its low-energy physics closely resembles that of the trilayer La₄Ni₃O₁₀, despite their differences in nominal filling, rather than the conventional bilayer La₃Ni₂O₇.